This invention relates to apparatus for trimming a plastic blow molding.
Plastic blow moldings conventionally utilized to provide containers for liquids or other contents are manufactured in one process by extruding a hollow tubular parison of hot plastic between open portions of a mold which is then closed prior to introducing air into the interior of the parison. The pressurized air blows the parison outwardly to the shape of an enclosed cavity defined by the closed mold portions so as to thereby provide a blow molding that can be removed after opening of the mold. Excess plastic referred to a flash is conventionally removed by a reciprocally removable knife in a guillotine fashion to further process the blow molding. At a dispensing neck of the blow molding for providing the container, further finish is usually required and is conventionally performed by a rotary reamer which produces plastic particles some of which can be received within the interior of the blow molding. These plastic particles must be removed prior to completion of the blow molded article which is usually performed by turning the blow molding upside down and blowing air into it so that the cooperation of gravity and the blowing air cleans the interior of the blow molding. These reaming and plastic particle removal operations add to the cost of the completed blow molded articles and thus must be borne by the ultimate consumer.
U.S. Pat. No. 5,167,968 discloses a finishing machine for trimming a blow molding by a rotary knife so as to thereby eliminate the problem involved with reaming as far as generating particles that are received within the blow molding so as to require removal. The cutting performed involves a mechanism that extends along the rotational axis into a cup member that receives the portion of the blow molding that is cut off during the trimming operation. A plunger that moves along the central axis ejects the trimmed portion from the cup member adjacent the location of cutting in preparation for the next cycle.
An object of the present invention is to provide improved apparatus for trimming a plastic blow molding and for facilitating removal of the trimmed off portion of the blow molding.
In carrying out the above object, apparatus for trimming a blow molding in accordance with the invention includes a trimmer head adjacent which is positioned the blow molding to be trimmed. A rotary trimming assembly of the apparatus has a generally annular shape and includes a rotary member rotatably supported by the trimmer head and rotatably driven about a central axis. The rotary member is axially fixed along the central axis with respect to the trimmer head and includes a tube through which the central axis extends with the tube generally in alignment with the blow molding to be trimmed. The rotary trimming assembly also includes a knife holder pivotally mounted on the rotary member for rotation therewith and being pivotally movable with respect thereto about a trimming axis that extends parallel to the central axis in a spaced relationship thereto. The rotary trimming assembly also includes an annular cam follower that is movable along the central axis with respect to the rotary member thereof that mounts the knife holder. The rotary trimming assembly further includes a cam mechanism that extends between the annular cam follower and the knife holder to pivot the knife holder upon movement of the annular cam follower along the central axis with respect to the rotary member such that a knife held by the knife holder trims a portion of the blow molding from the rest of the blow molding. An actuating mechanism of the apparatus includes a cam that is mounted by the trimmer head and that engages the annular cam follower of the rotary trimming assembly during rotary driving thereof about the central axis. The actuating mechanism includes an actuator that moves the cam thereof to move the annular cam follower of the rotary trimming assembly and pivot the knife holder such that the knife held thereby trims the portion of the blow molding to allow the trimmed blow molding portion to move through the tube away from the trimmed blow molding in preparation for the next trimming cycle.
The construction and operation of the apparatus thus not only provides for convenient trimming of the blow molding but also facilitates removal of the trimmed blow molding portion for movement away from the location of trimming such that the apparatus can be conveniently prepared for the next trimming cycle.
In the preferred construction of the apparatus, an operator moves the trimmer head toward the blow molding for the trimming operation and back away from the trimmed blow molding in preparation for the next cycle.
The apparatus also includes a conduit connected to the tube of the rotary trimming assembly and further includes a vacuum source for drawing a vacuum in the conduit to move the trimmed blow molding portion through the conduit away from the trimmer head in preparation for the next trimming cycle. The vacuum source is preferably a blower having an output. A Y coupling of the apparatus has a venturi and is connected to the conduit and to the output of the blower to draw the vacuum that moves the trimmed blow molding portion through the conduit away from the trimmer head.
The head includes first and second mounting blocks. The rotary member of the rotary trimming assembly includes a ring portion rotatably supported by the first mounting block of the trimmer head, and the tube of the rotary member of the rotary trimming assembly has one end that projects from the ring portion of the rotary member toward the blow molding to be trimmed, and the tube has another end rotatably supported by the second mounting block. Antifriction bearings rotatably support the ring portion and the tube of the rotary member on the first and second mounting blocks.
The apparatus also has the tube of the rotary member slidably supporting the annular cam follower at a location between the first and second mounting blocks for movement along the central axis under the impetus of the cam of the actuating mechanism to perform the trimming operation. The knife holder preferably has an elongated shaft that extends along the trimming axis and has an intermediate portion that is pivotally supported on the ring portion of the rotary member. The elongated shaft of the knife holder has a first end that projects from the ring portion of the rotary member toward the blow molding to be trimmed and includes a knife portion holder that holds the knife for trimming the blow molding. The elongated shaft of the knife holder also has a second end that projects from the ring portion of the rotary member toward the annular cam follower and has slide connections therewith where the cam mechanism of the rotary trimming assembly pivots the elongated shaft of the knife holder upon movement of the annular cam follower under the impetus of the actuating mechanism. A pair of guideways extend from the ring portion of the rotary member of the trimming assembly and have slide connections that support the annular cam follower of the rotary trimming assembly for movement along the central axis. A support plate is connected to the pair of guideways and has a bushing for rotatably supporting the second end of the knife holder shaft. The cam mechanism of the rotary trimming assembly includes a cam pin supported by the annular cam follower and also includes a cam follower slot that receives the cam pin and is located in the second end of the elongated shaft of the knife holder.
In its preferred construction, the apparatus includes a driven member mounted on the tube of the rotary member to provide rotary driving thereof for the trimming operation. This driven member is most preferably a belt pulley mounted on the tube of the rotary member at a location between the annular cam follower of the rotary trimming assembly and the second mounting block that rotatably mounts the tube on the trimmer head.
The preferred construction of the actuating mechanism of the apparatus includes a fork pivotally mounted on the trimmer head. This fork includes a pair of arms having distal ends between which is located the annular cam follower of the trimming assembly. The cam of the actuating mechanism includes a pair of cam rollers that are respectively rotatably supported on the distal ends of the pair of arms of the fork. The annular cam follower of the trimming assembly has a pair of annular flanges that are spaced along the central axis to receive the pair of cam rollers therebetween, and the fork of the actuating mechanism includes a leg that is moved by the actuator to move the cam rollers and the annular cam follower of the rotary trimming assembly to pivot the knife holder and perform the trimming operation.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.